The implementation of a commercially available multi-gene profile test for breast cancer characterization in a department of pathology: what have we learned from the first 100 cases?

Analysis of breast cancer prognostic and predictive factors is still nowadays poorly accurate and standardized. The advent of multi-gene expression profiles (MGEPs) has improved the prediction of breast cancer outcome, particularly regarding early luminal breast cancers (LBCs). The availability in our Institute of EndoPredict® (EP), a last-generation prognostic gene signature assay, has prompted us to study a series of LBCs, firstly verifying its reproducibility on six routine representative cases, either presenting non-optimal preanalytical conditions or different tumor samples from the same patient; secondly, correlating EP results on 8 retrospectively recruited samples with patients' follow-up; thirdly, applying prospectively EP on 100 routinely diagnosed cases, assessing the oncologists' and pathologists' attitude toward it. The complete reproducibility of EP on all the samples investigated in the first phase allowed to state that EP overcomes the detrimental effects of an inaccurate pre-analytic phase, determining the most appropriate prognostic and predictive parameters of breast cancer. The second phase confirmed EP as a fundamental tool in guiding therapeutic decision, improving the classical bio-pathological characterization and recovering 38% patients' inadequately managed. Finally, the study disclosed how oncologists sometimes inadequately requested EP, but also how it allows a better stratification of breast cancer otherwise considered poorly aggressive and not requiring an EP test, such as G1 neoplasms or tubular histotype. In conclusion, the introduction of EP test in an Anatomic Pathology Department emerges as a useful tool in routine breast cancer diagnosis, both for the characterization of individual cases and, as a result, for more appropriate therapeutic choices.